DESCRIPTION: (Applicant's Description) Neovascularization is the major cause of vision loss in patients with age- related macular degeneration (AMD), diabetic retinopathy, and retinopathy of prematurity. AMD is the leading cause of blindness in the Western world in individuals over 60 years of age. Since a large proportion of the population is living well beyond this age, this is a significant threat to the quality of life in elderly people. In patients with AMD new vessel growth (angiogenesis) beneath the retina from the underlying choroid (choroidal neovascularization or CNV) is the major or cause of severe visual loss in these patients. We recently examined the role of apoptosis in controlling new vessel growth in the eye by examining the function of two molecules, Fas (CD95) and FasL (CD95L). Our studies revealed that FasL plays a significant role in controlling CNV, where FasL+ retinal pigment epithelial cells (RPE) prohibit the growth and development of new Fas+ subretinal vessels that damage vision. Studies described in this proposal are designed to thoroughly understand the role of Fas/FasL and apoptosis in the pathogenesis of AMD. We propose 5 aims. Aim 1 we will more completely evaluate the role of Fas/FasL in CNV in a mouse model using normal, Fas, and FasL defective mice. In Aim 2 we will study cell endothelial cells derived from the choroid and compare these to endothelial cells derived from other areas. We will examnine cell death, proliferation, and differentiation using in vitro models and characterize the role of the Fas antigen in these processes. Aim 3 will contains experiments to explore the function of FasL on RPE cells and determine how growth factors and MMP inhibitors can affect FasL function in these cells that are crucial in controlling CNV. Aim 4 will explore potential treatment modalities in CNV applying the knowledge we have gained concerning the regulation of FasL expression to the animal model. Finally, studies in Aim 5 will evaluate clinical specimens from patients AMD for Fas/FasL expression. Our studies should provide important insights into one of the leading causes of blindness in the western world.